This is the 17364th most frequent Russian word.
твои
"Твои" means "your" (plural or informal singular possessive form).
In this sentence, 'твои' is the plural form of the possessive pronoun for 'you', used to indicate possession of 'books'.
Твои книги лежат на столе.
Your books are on the table.
Here, 'твои' is used to describe multiple friends that belong to someone being addressed informally.
Где твои друзья?
Where are your friends?
In this case, 'твои' is utilized to show possession of the plural noun 'photographs', referring to the person being spoken to.